Items with wire actuators

ABSTRACT

An item such as a fabric-based item or other item may have one or more actuators. An actuator may have a conductive strand of material. A control circuit may supply a current to the conductive strand that induces a length change in the conductive strand due to ohmic heating and associated thermal expansion effects. The control circuit may be used to activate the actuator in response to user input that is supplied to an associated input device such as a switch, capacitive sensor, force sensor, light-based sensor, or other input component. The fabric-based item may include fabric such as woven fabric or knit fabric. Strands of conductive material may serve as signals paths for supplying current to conductive strands in actuators. Magnetic-field-based actuators may be formed by coiling conductive strands around tubular support structures such as piping in fabric-based items.

This application is a divisional of U.S. patent application Ser. No.15/448,832, filed Mar. 3, 2017, which claims the benefit of provisionalpatent application No. 62/311,600, filed Mar. 22, 2016, both of whichare hereby incorporated by reference herein in their entireties.

FIELD

This relates generally to actuators and, more particularly, to actuatorsfor items such as items with fabric.

BACKGROUND

Cellular telephones and other devices sometimes include vibratingactuators. An actuator formed from a motor with a rotating eccentricmass may be used, for example, to provide a vibrating alert when anincoming telephone call is received. Actuators may also be used toprovide haptic feedback for displays, touch pads, or other inputdevices.

If care is not taken, actuators may be too bulky, may consume more powerthan desired, or may not be compatible with the structures used informing an item of interest.

SUMMARY

An item such as a fabric-based item or other item may have one or moreactuators. The actuators may be used to provide a user of an item withhaptic output. For example, in an item such as a fabric coveredkeyboard, keys may be provided with actuators so that haptic feedbackmay be provided as a user presses the keys.

An actuator may have a conductive strand of material. When it is desiredto activate the actuator, a control circuit may supply a current to theconductive strand. The current may heat the conductive strand throughohmic heating and may thereby increase the length of the conductivestrand due to thermal expansion effects. When the current is removed,the conductive strand may rapidly cool and contract. Changes in thelength of the conductive strand may supply haptic output.

A control circuit in an item may be used to activate an actuator inresponse to user input that is supplied to an associated input devicesuch as a switch, capacitive sensor, force sensor, light-based sensor,or other input component that is aligned with the actuator. Thefabric-based item may include fabric such as woven fabric or knitfabric. Strands of conductive material may serve as signals paths forsupplying current to conductive strands in actuators.

Magnetic-field-based actuators may be formed by coiling conductivestrands around cylindrical support structures such as piping in afabric-based item. The cylindrical support structure may initially havea non-circular cross-sectional shape such as an oval shape. When currentis applied to a coiled conductive strand, the coiled conductive strandmay assume a circular cross-sectional shape. The change in shape of theactuator due to the applied current may serve as haptic output for auser.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative item of the type thatmay be provided with one or more actuators in accordance with anembodiment.

FIG. 2 is a diagram of an illustrative actuator and associated controlcircuitry in accordance with an embodiment.

FIG. 3 is a diagram showing illustrative control signals that may beprovided to an actuator in accordance with an embodiment.

FIG. 4 is a diagram showing illustrative changes in the properties of anactuator such as actuator length in response to the control signal ofFIG. 3 in accordance with an embodiment.

FIGS. 5, 6, and 7 are cross-sectional side views of illustrative strandsof material that may be used in forming an actuator in accordance withan embodiment.

FIG. 8 is a cross-sectional side view of a layer of woven fabric inaccordance with an embodiment.

FIG. 9 is a top view of an illustrative layer of knit fabric inaccordance with an embodiment.

FIG. 10 is a perspective view of an illustrative layer of material intowhich a length of wire for an actuator has been incorporated inaccordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative item with anactuator and other circuitry in accordance with an embodiment.

FIGS. 12 and 13 are top views of illustrative woven fabric layers havingsignal paths for providing control signals to actuators in accordancewith embodiments.

FIG. 14 is a top view of an illustrative electronic device havinglengths of wire that serve as actuators in accordance with anembodiment.

FIG. 15 is a cross-sectional side view of an illustrative actuatorhaving a moving member that is controlled by a wire actuator inaccordance with an embodiment.

FIG. 16 is a cross-sectional side view of an illustrative actuatorhaving wires embedded in a layer of material in accordance with anembodiment.

FIG. 17 is a side view of an illustrative loop of wire in an actuator inaccordance with an embodiment.

FIG. 18 is a side view of the loop of wire of FIG. 17 followingapplication of current to the wire to change the shape of the wire inaccordance with an embodiment.

FIG. 19 is a perspective view of an oval tube structure such as a lengthof piping on a fabric layer with an actuator formed from a coiled wirein accordance with an embodiment.

FIGS. 20 and 21 are cross-sectional side views of illustrativemultilayer fabric layers having wires for actuators in accordance withembodiments.

DETAILED DESCRIPTION

It may be desirable to provide an electronic device or other item withactuators. Actuators may be used to provide tactile output to a user ofa device. For example, haptic feedback may be provided to a user inconnection with a key press event or a tactile alert may be generated.

An illustrative item of the type that may be provided with one or moreactuators is shown in FIG. 1. Item 10 of FIG. 1 may be an electronicdevice or an accessory for an electronic device such as a laptopcomputer, a computer monitor containing an embedded computer, a tabletcomputer, a cellular telephone, a media player, or other handheld orportable electronic device, a smaller device such as a wristwatchdevice, a pendant device, a headphone or earpiece device, a deviceembedded in eyeglasses or other equipment worn on a user's head, orother wearable or miniature device, a television, a computer displaythat does not contain an embedded computer, a gaming device, anavigation device, an embedded system such as a system in which item 10is mounted in a kiosk, in an automobile, airplane, or other vehicle,other electronic equipment, or equipment that implements thefunctionality of two or more of these devices. If desired, item 10 maybe a removable external case for electronic equipment, may be a strap,may be a wrist band or head band, may be a removable cover for a device,may be a case or bag that has straps or that has other structures toreceive and carry electronic equipment and other items, may be anecklace or arm band, may be a wallet, sleeve, pocket, or otherstructure into which electronic equipment or other items may beinserted, may be part of a chair, sofa, or other seating (e.g., cushionsor other seating structures), may be part of an item of clothing orother wearable item (e.g., a hat, belt, wrist band, headband, shirt,pants, shoes, etc.), or may be any other suitable item with one or moreactuators.

In some arrangements, item 10 may include intertwined strands ofmaterial 12 that form fabric. The strands of material in item 10, whichmay sometimes be referred to herein as yarns, may be single-filamentstrands (sometimes referred to as fibers or monofilaments) or may bestrands of material formed by intertwining multiple monofilaments ofmaterial together. The strands of material may be formed from one ormore layers of dielectric such as plastic, glass, etc. and/or one ormore layers of conductive material such as metal, conductive polymermaterials, polymer with sufficient embedded electrically conductivefiller material to render the polymer conductive, graphene, or otherconductive substances. Strands 12 that include metal may sometimes bereferred to as wires.

Fabric formed from strands 12 may form all or part of a housing wall orother layer in an electronic device, may form internal structures in anelectronic device, may form clothing, may form a strap, may form a wallfor a bag or other enclosure, or may form other fabric-based structures.Item 10 may be soft (e.g., item 10 may have a fabric surface that yieldsto a light touch), may have a rigid feel (e.g., the surface of item 10may be formed from a stiff fabric), may be coarse, may be smooth, mayhave ribs or other patterned textures, and/or may be formed as part ofan item that has portions formed from non-fabric structures of plastic,metal, glass, crystalline materials, ceramics, or other materials.

Strands 12 may be formed from polymer, metal, glass, graphite, ceramic,natural materials such as cotton or bamboo, or other organic and/orinorganic materials and combinations of these materials. Conductivecoatings such as metal coatings may be formed on non-conductivematerial. For example, plastic strands 12 in a fabric layer may becoated with metal to make them conductive. Reflective coatings such asmetal coatings may be applied to make strands reflective. Strands may beformed from bare metal wires or metal wire intertwined with insulatingmonofilaments (as examples). Bare metal strands and strands of polymercovered with conductive coatings may be provided with insulating polymerjackets.

Strands 12 may be intertwined to form fabric using intertwiningequipment such as weaving equipment, knitting equipment, or braidingequipment. Intertwined strands may, for example, form knitted fabric orwoven fabric. Conductive strands and strands with insulating surfacesmay be woven, knit, or otherwise intertwined to form conductive paths.The conductive paths may be used in forming signal paths (e.g., signalbuses, power lines, control signal interconnects, etc.) and may be usedin forming part of sensors (e.g., capacitive touch sensor electrodes,resistive touch sensor electrodes, etc.). To provide a user with tactile(haptic) output, conductive strands of material may be used in formingactuators. In general, conductive strands 12 in a fabric or otherstructure may be used in carrying power signals, digital signals, analogsignals, sensor signals, control signals, data, input signals, outputsignals, or other suitable electrical signals.

Item 10 may include additional mechanical structures 14 such as polymerbinder to hold strands 12 in a fabric or other structure together,support structures such as frame members, housing structures (e.g., anelectronic device housing), and other mechanical structures.

To enhance mechanical robustness and electrical conductivity atstrand-to-strand connections, additional structures and materials 14(e.g., solder, crimped metal connections, welds, conductive adhesivesuch as anisotropic conductive film and other conductive adhesive,non-conductive adhesive, fasteners, etc.) may be used to help formstrand-to-strand connections. These strand-to-strand connections may beformed where strands 12 cross each other perpendicularly or at otherstrand intersections where connections are desired. Insulating materialcan be interposed between intersecting conductive strands at locationsin which it is not desired to form a strand-to-strand electricalconnection. The insulating material may be plastic or other dielectric,may include an insulating strand or a conductive strand with aninsulating coating, etc. Solder connections may be formed betweenconductive strands by melting solder so that the solder flows overconductive strands. The solder may be melted using an inductivesoldering head to heat the solder, using a reflow oven to heat thesolder, using a laser or hot bar to heat the solder, or using othersoldering equipment. During soldering, outer dielectric coating layers(e.g., outer polymer layers) may be melted away in the presence ofmolten solder, thereby allowing underlying metal strands to be solderedtogether.

Item 10 may include circuitry 16. Circuitry 16 may include electricalcomponents that are coupled to fabric or other structures formed fromstrands 12, electrical components that are housed within an enclosurethat includes fabric or other structures formed from strands 12,electrical components that are attached to fabric formed from strands 12using welds, solder joints, conductive adhesive bonds, crimpedconnections, or other electrical and/or mechanical bonds, and electricalcomponents mounted in electronic device housings formed from plastic,glass, metal, fabric, and/or other materials. Circuitry 16 may includemetal structures for carrying current, electrical devices such asintegrated circuits, light-emitting diodes, sensors, and switches, andother electrical components. Circuitry 16 may include one or moreactuators such as one or more actuators formed using conductive strands12. The actuators may be aligned with respective electrical componentsin circuitry 16 and item 10. For example, each actuator in circuitry 16may be aligned with a respective switch, sensor, or other inputcomponent. Control circuitry in circuitry 16 may be used to control theoperation of item 10.

Item 10 may interact with electronic equipment or other additional items18. Items 18 may be attached to item 10 or item 10 and item 18 may beseparate items that are configured to operate with each other (e.g.,when one item is a case and the other is a device that fits within thecase, when one item is a wrist watch or pendant device and the otheritem is a strap for the item, etc.). Control circuitry in circuitry 16may be used to support communications with item 18 and/or other devices.Circuitry 16 may include antennas and other structures for supportingwireless communications with item 18. Item 18 may also interact withitem 10 using a wired communications link or other connection thatallows information to be exchanged.

In some situations, item 18 may be an electronic device such as acellular telephone, computer, or other portable electronic device anditem 10 may form a cover (e.g., a cover including a keyboard and/orother buttons or a cover that does not include a keyboard), a case, abag, an item of clothing, or other structure that receives theelectronic device in a pocket, an interior cavity, or other portion ofitem 10. In other situations, item 18 may be a wristwatch device orother electronic device and item 10 may be a strap or other fabric-baseditem that is attached to item 18 (e.g., item 10 and item 18 may togetherform a fabric-based item such as a wristwatch with a strap). In stillother situations, item 10 may be an electronic device, fabric 12 may beused in forming the electronic device, and additional items 18 mayinclude accessories or other devices that interact with item 10. Signalpaths formed from conductive strands may be used to route signals initem 10 and/or item(s) 18.

The fabric that makes up item 10 may be formed from multifilament and/ormonofilament yarns that are intertwined using any suitable intertwiningequipment (knitting equipment, weaving equipment, braiding equipment,equipment for forming felt, etc.). The fabric may be knitted, woven,braided, or otherwise formed from intertwined strands 12. Woven fabricmay have a plain weave, a basket weave, a satin weave, a twill weave, orvariations of these weaves, may be a three-dimensional woven fabric, ormay be other suitable fabric. Knitted fabric may be weft knitted or warpknitted.

To provide tactile output to a user of item 10, item 10 may have one ormore actuators. The actuators may be formed from one or more conductivestrands of material. When current is applied to a conductive strand ofmaterial, the strand of material heats through ohmic heating. This causethe conductive strand to change shape and thereby create a force that isdetectable by a user's fingertips or other body part. Current may beapplied to the entire conductive strand of material (e.g., from a nodeat one end of the strand to a node at the other end of the strand) ormay be applied to a segment of a conductive strand (e.g., between firstand second nodes located at two different respective points along thelength of the strand).

As shown in FIG. 2, circuitry 16 of item 10 may include controlcircuitry 40. Control circuitry 40 may supply control signals toactuator 52 using conductive paths such as paths 44. Paths 44 may beformed from one or more conductive strands 12 and/or other conductivestructures (e.g., conductive housing structures, metal plates, strips ofmetal foil, traces on printed circuits, metal brackets, etc.). Actuator52 may have one or more conductive strands such as illustrativeconductive strand 42 of FIG. 2. As shown in the example of FIG. 2,strand 42 may extend along longitudinal axis 50 and may have at least aportion of length L (i.e., strand 42 has opposing ends and ischaracterized by a length L extending between these ends or strand 42represents a segment of length L within a longer strand extending alongaxis 50). Configurations in which strand 42 of actuator 52 is astand-alone strand of length L may sometimes be described herein as anexample, but, in general, actuator 52 may include one or more strands 42of length L that are portions of larger strands of material. Strand 42may be formed from a segment of material such as a wire or yarn formedfrom multiple monofilaments that have been intertwined together (asexamples). Other configurations for strand 42 may be used, if desired.

Strand 42 may be formed from a material such as metal (e.g., anelemental metal such as platinum, an alloy such as nickel-chrome, etc.)or other conductive material. When current is applied to strand 42,ohmic heating will cause the temperature of strand 42 to rapidly rise.This will cause the material of strand 42 to expand due to thermalexpansion effects (when the material of strand 42 has a positivecoefficient of thermal expansion) or will cause the material of strand42 to contract (when the material of strand 42 has a negativecoefficient of thermal expansion). For example, assuming a positivecoefficient of thermal expansion for strand 42, application of currentto strand 42 by control circuitry 40 and paths 44 will cause the lengthL of strand 42 to increase in directions 46. Upon removing the appliedcurrent, air or other material surrounding strand 42 will cause strand42 to cool and contract in directions 48 (i.e., length L may shrink).Changes in the length L of strand 42 along longitudinal axis 50 ofstrand 42 (i.e., elongations of strand 42) can be sensed by a user'sfinger or other body part that is in contact with strand 42. The rise intemperature of strand 42 and the subsequent cooling of strand 42 tend tobe more difficult for a user to sense than the shear forces and otherforces on the user's finger that are produced by changes in length L indirections 46 and 48. Accordingly, actuator 52 is generally effective atproducing haptic output due to the ability of actuator 52 to producedimensional changes such as length changes (i.e., longitudinalexpansions and contractions in response to pulses of current).

Strand 42 may have any suitable size. As an example, length L of strand42 (i.e., the length of the heated portion of a strand) may be 1-100 mm,may be 5-10 mm, may be 2-30 mm, may be more than 5 mm, more than 10 mm,less than 15 mm, less than 10 mm, or other suitable length. The diameterof strand 42 may be about 0.05 to 0.1 mm, 0.03 to 0.2 mm, more than 0.05mm, more than 0.1 mm, less than 0.15 mm, or other suitable diameter. Theconductive material that forms strand 42 may have a resistance of 1-3ohm/cm, more than 0.5 ohm/cm, less than 5 ohm/cm, or other suitablevalue. Paths 44 may have a resistance that is less than the resistanceof strand 42, so that strand 42 is heated rapidly without heating paths44 or, if desired, paths 44 may have other resistance values.

The control signal that control circuitry 40 applies to strand 42 mayinclude one or more pulses 54 of current I of the type shown in FIG. 3(e.g., pulses with a duration T of about 1-10 ms, more than 3 ms, lessthan 20 ms, or other suitable pulse width), resulting in noticeablechanges in strand length L (i.e., elongation of the heated strandmaterial) and/or strand diameter, as shown in FIG. 4.

As shown in the illustrative cross-sectional side view of strand 42 ofFIG. 5, strand 42 may be formed from a solid conductive material (e.g.,strand 42 may be formed from an elemental metal or a metal that is analloy). FIG. 6 shows how strand 42 may have a coating layer such ascoating 42-2 on a core such as core 42-1. Core 42-1 may be a metal orother conductive material and coating 42-2 may be a polymer or otherdielectric or, if desired, core 42-1 may be a polymer or otherdielectric and coating 42-2 may be a metal coating layer or otherconductive coating layer. Configurations in which layers 42-1 and 42-2are both metals or are both other conductive materials may also be used.In the illustrative configuration of FIG. 7, strand 42 has threeportions: 42A, 42B, and 42C. Core 42A, which may be formed from metal orwhich may be formed from polymer or other dielectric, inner coating 42B,which may be formed from metal or which may be formed from polymer orother dielectric, and outer coating 42C, which may be formed from metalor which may be formed from polymer or other dielectric. Additionalcoating layers of polymer and/or metal may also be formed on the layersof strand 42 in FIG. 7. One or more, two or more, or three or more ofthe layers of material in strand 42 of FIG. 7 may be formed from aconductive material such as metal (elemental or alloy) so that currentmay pass through strand 42 during actuation of actuator 52.

FIG. 8 is a cross-sectional side view of an illustrative fabric. Fabric20 of FIG. 8 is a woven fabric formed from strands 12. Strands 12 mayinclude warp strands 12A and weft strands 12B. Each strand 12 maycontain one or more monofilaments of material (see, e.g., illustrativemonofilament strands 26). As shown in FIG. 9, fabric 20 may be a knitfabric. In the illustrative configuration of FIG. 9, fabric 20 has asingle layer of knit strands 12 that form horizontally extending rows ofinterlocking loops (courses 22) and vertically extending wales 24. Otherfabric constructions may be used for fabric 12 if desired.

Strands of material for actuator 52 such as illustrative strand 42 ofFIG. 7 may be incorporated into fabric 20 (e.g., by weaving one or morestrands such as strand 42 into fabric 20 as a warp or weft strand inplace of one of the warp or weft strands 12 of FIG. 8 or by knitting oneor more strands such as strand 42 into fabric 20 in place of one ofstrands 12 of FIG. 9). Strands of material such as illustrative strand42 may also be incorporated into fabric 20 by sewing or othertechniques. As shown in FIG. 10, for example, strand (strand segment) 42of length L may be sewn into layer 20 or otherwise incorporated intolayer 20. Layer 20 of FIG. 10 may be a layer of fabric and/or one ormore other layers of material such as plastic, leather, metal foil, etc.

FIG. 11 is a cross-sectional side view of item 10 in an illustrativeconfiguration in which item 10 includes layer(s) of material such asfabric 20 that form walls for item 10 or other portions of item 10(e.g., straps, handles, pockets, etc.). Item 10 may include circuitry16. Circuitry 16 may include components in interior 70 of item 10 suchas electrical components 74. Components 74 may be mounted on one or moresubstrates such as printed circuit board 72 and/or may be soldered,crimped, welded, or otherwise attached to conductive strands 12 infabric 20. Printed circuit board 72 may be a rigid printed circuit board(e.g., a printed circuit board formed from rigid printed circuit boardsubstrate material such as fiberglass-filled epoxy) or may be a flexibleprinted circuit (e.g., a printed circuit formed from a sheet ofpolyimide or other flexible polymer substrate material). Components 74may include integrated circuits and other components.

One or more actuators may be incorporated into item 10. In the exampleof FIG. 11, actuator 52 is incorporated into a portion of fabric 20 in alocation that can be touched by a user's finger (see, e.g., finger 60).This location may overlap a component such as component 68 of circuitry16 (i.e., actuator 52 may be aligned with component 68). Component 68may be mounted to printed circuit 72 or may be coupled to cables orother signal paths in item 10. Components such as component 68 mayinclude light-emitting components, may include input devices such asswitches (e.g., a switch for a keyboard key or a switch for astand-alone button, capacitive sensors that serve as touch sensors orcapacitive buttons, force sensors such as force sensors based on straingauges or other structures, light-based input devices such aslight-based touch sensors or light-based proximity sensors, other inputdevices, or other suitable electrical devices). As shown in FIG. 11,component 68 or a light-emitting diode associated with component 68 mayemit light 66 that is visible to a user such as viewer 62 who is viewingitem 10 in direction 64. Because actuator 52 is aligned with component68, actuator 52 can provide tactile output to finger 60 when finger 60is adjacent to component 68 (e.g., when finger 60 is supplying input toan input device). Other types of arrangement may be used for item 10 ifdesired. The arrangement of FIG. 11 in which components such ascomponent 68 are aligned with actuators 52 is merely an example.

With one illustrative configuration for item 10, components such ascomponent 68 may be used to form a keyboard with illuminated keys. Forexample, item 10 may be a cover for a tablet computer or other devicethat includes a keyboard and each component 68 may include a dome switchor other switch for a respective keyboard key in the keyboard. With thisarrangement, each component 68 may be associated with a light-emittingdiode or other light-emitting structure that emits light 66 in a trimpattern for the keyboard key and/or in the shape of a symbol that servesas a label for the key.

During operation, a user may place fingers on the keyboard such asillustrative finger 60 of FIG. 11 and may push downwards on the keyboard(item 10 in this example). The downward pressure from finger 60 mayclose the dome switch or may activate the capacitive sensor device,force sensor device, light-based sensor, or other component 68 thatsenses user key press activity. To provide the user with tactilefeedback (sometimes referred to as haptic feedback), control circuitry40 (FIG. 2) of circuitry 16 may actuate actuator 52 in response todetection of the closing of the dome switch or other input device statechange indicating detection of a key press event. Circuitry 40 may, forexample, supply one or more current pulses to a conductive strand. Ascontrol circuitry 40 supplies one or more current pulses to strand 42 ofactuator 52, actuator 52 will change shape and this physical change inthe state of actuator 52 will be detected by the user at finger 60 as ashear force or other physical force. The use of haptic feedback in thisway may provide the user with confirmation that the user successfullypressed a desired key. In general, any type of force sensor, capacitivetouch sensor, light-based sensor, switch, or other user input device maybe provided with haptic feedback structures based on one or more ofactuators 52. The use of actuator 52 to provide a fabric keyboard keywith haptic feedback is merely illustrative.

FIG. 12 is a top view of a portion of a fabric layer in which strand 42of actuator 52 has been coupled to conductive strands 44 in a fabricmade up of other strands 12 (e.g., insulating strands). Strands 44 maybe formed from metal that is more conductive than the metal of strand 42(as an example). At connection points such as connections 76, solder,welds, crimped connections, or other connection structures may be usedto join and electrically short strands 44 to strand 42, which may be astand-alone length of material or which may be a segment of a longerstrand. During operation of actuator 52, current may be applied tostrand 42 from control circuitry 40 (FIG. 2) using strands 44 andconnections 76. Because strands 44 are more conductive per unit lengththan strand 42 (in this example), there will be less heating in strands44 (e.g., between nodes P and Q and between nodes R and S) than instrand 42 between nodes Q and R.

If desired, strands 44 may be collinear with strand 42 (i.e., strand 42may be a resistive segment of conductive material within a longer strandformed up of less resistive conductive material), as shown inillustrative fabric 20 of FIG. 13. In this type of arrangement, therewill be less ohmic heating in strands 44 between nodes A and B andbetween nodes C and D than in strand 42 between nodes B and C due to thelower resistance per unit length of strands 44 than strand 42.

In the illustrative configuration of item 10 shown in the top view ofFIG. 14, item 10 is an electronic device having electronic devicehousing 78. Housing 78 may be formed form metal, plastic, glass,ceramic, fiber-composite materials, and/or other materials. Strands 42may be coupled to different locations on housing 78 (e.g., strands 42may be coupled to housing 78 directly or may be coupled to housing 78indirectly through structures that are coupled to housing 78). Whencurrent is passed through strands 42, the change in length of strands 42will cause housing 78 to vibrate or otherwise move and provide hapticoutput for item 10 (i.e., strands 42 will serve as actuators 52).Strands 42 may lengthen or may contract in response to applied current,depending on whether strands 42 exhibit a positive or negativecoefficient of thermal expansion.

If desired, actuators 52 may be arranged in rows, in columns, in otherlinear one-dimensional arrays, in curved strips, in two-dimensionalarrays with rectangular outlines, in arrays with circular outlines, inarrays having shapes with curved and/or straight edges, or in otherarrangements on the surface of a fabric in item 10 and/or elsewhere initem 10. Actuators 52 may be activated in patterns by control circuitry40. Different patterns may be used in different contexts. For example,control circuitry 40 may direct actuators 52 to produce a first patternof haptic output in response to satisfaction of a first set of operatingconditions and to produce a second pattern of haptic output in responseto satisfaction of a second set of operating conditions.

Item 10 may include a series of actuators 52 that extend along a givendimension in item 10 (e.g., in a row along the surface of a fabric,etc.). With this type of arrangement, each actuator 52 may bemomentarily actuated in sequence to create a wave-like haptic effect.Actuators 52 may, for example, be operated in sequence to generate awave of fabric displacement that passes from left-to-right across item10. Actuators 52 may also be synchronized so as to generate a wave thatmoves in other directions, may be used to generate oscillating output ata given position (e.g., pulses of displacement in a stationarylocation), or may create haptic output in other patterns across thesurface of item 10. Control circuitry 40 may create timed pulses ofcurrent to produce effects such as these or other haptic outputpatterns.

FIG. 15 is a cross-sectional side view of actuator 52 in an illustrativeconfiguration in which strand 42 is attached to a movable member such asmember 80 to provide actuator 52 with mechanical advantage (i.e., toprovide leverage). Strand 42 may have one end coupled to supportstructure 92 and another end coupled to member 80. Member 80 may pivotabout hinge 94. Tip 88 of member 80 may be covered with fabric 20 orother covering structures. A user's finger such as finger 60 may touchtip 88 of member 80 through fabric 20 and may thereby sense whetheractuator 52 is active (i.e., whether tip 88 is moving). When no currentis applied to strand 42 by control circuitry 40 (FIG. 2), strand 42 hasa constant length and spring 84 may bias member 80 downwards indirection 86 until strand 42 has reached its maximum room temperaturelength, thereby preventing further downward movement of member 80. Inthis configuration, member 80 and tip 88 do not move and the user'sfinger 60 will not sense any movement in tip 88 of actuator 52. Whencurrent is applied to strand 42 by control circuitry 40, strand 42 mayincrease in length due to the rise in temperature of strand 42 fromohmic heating. This allows spring 84 to pull member 80 farther downwardsin direction 86.

Due to the position of strand 42 near pivot 82 and the relatively longlength of member 80 between pivot 82 and tip 88, small changes in thelength of strand 42 will give rise to relatively larger changes in theposition of tip 88. In particular, tip 88 may move downwards indirection 90 by more than the increase in length of strand 42. Thiscauses finger 60 to experience enhance movement in actuator 52. Ifdesired, other types of lever arm structures may be used to provideactuator 52 with mechanical advantage to amplify the vibrational output(or other movement) of actuator 52 in response to application of a givenamount of current to strand 42. The configuration of FIG. 15 is merelyillustrative. Actuator 52 may form part of a keyboard key in afabric-based item such as a fabric cover for a tablet computer, may formpart of an electronic device housing (e.g., a portion of a housingassociated with a button for which it is desired to provide hapticfeedback), or may be formed as part of other items (e.g., fabric baseditems such as straps for watches, handles for bags, clothing, etc.), ormay be used in any other suitable item.

In the example of FIG. 16, item 10 includes a coating layer such aslayer 98 on a structure such as support structure 96. Support structure96 may form part of a fabric-based item (e.g., structure 96 may beformed from a layer of fabric 20) or may be an electronic device housingstructure or other suitable supporting structure. Coating layer 98 maybe formed from a layer of dielectric such as a polymer or other materialthat contains embedded filler structures such as particles 100. One ormore strands such as strands 42 may be embedded within layer 98. Thepolymer or other dielectric material of layer 98 may help electricallyinsulate strands 42 and/or may help protect strands 42 from damage.Layer 98 may be formed from an elastomeric material (e.g., silicone) toallow strands 42 to stretch and create shear forces that are detectableby finger 60. Filler 100 may include particles or fibers with highthermal conductivity (e.g., graphite, metal, etc.) to help enhance thethermal conductivity of layer 98. This may help strands 42 to rapidlycool after each pulse of current is applied to strands 42. Structure 96(e.g., a metal structure) may also serve as a heat sink that helpsremove heat from strands 42.

In some arrangements, conductive strands 12 may be arranged in a loopshape and may operate by creating magnetic fields that move theconductive strands. Initially, actuator 52 may have a strand such asstrand 102 of FIG. 17 that has a non-circular shape such as an ovalshape. When current is applied to a loop-shaped strand such as strand102 of FIG. 17, magnetic field B builds up within the interior of theloop. In the presence of magnetic field B within the interior of theloop, the shape of the loop tends to become circular to minimizepotential energy in the system, as shown in FIG. 18. The change in shapeof strand 102 from the oval (non-circular) coil shape of FIG. 17 to thecircular coil shape of FIG. 18 and the movement of strand 102 thatresults from this change of shape is detectable by a user's finger (see,e.g., finger 60 of FIG. 18). Because actuator 52 of FIGS. 17 and 18operates by producing magnetic fields B, actuators such as actuator 52of FIGS. 17 and 18 may sometimes be referred to as magnetic-field-basedactuators or coiled strand actuators.

If desired, a coiled strand actuator may be formed by coiling strand 102around a tubular structure such as tubular support structure 104 of FIG.19. Tubular support structure 104 may be a fabric structure such as alength of fabric piping and may, if desired, be attached to fabric 20(e.g., to serve as trim on fabric 20 in item 10). In general, tubularstructure (tube) 104 may be formed from any suitable materials (foam,fabric, elastomeric polymer, or other materials). Tubular structure 104may initially have an oval profile (e.g., a cross-sectional shape thatis characterized by a minor axis 106 and larger major axis 108) or othernon-circular profile. When current is applied to strand 102, thenon-circular cross-sectional shape of structure 104 will tend to changeto a circular cross-sectional shape, as described in connection withactuator 52 of FIGS. 17 and 18. This will create movement in tubularstructure 104 that can be detected by a user's finger or other body partthat is touching tubular structure 104 (i.e., tubular structure 104 andcoiled strand 102 will form actuator 52).

FIGS. 20 and 21 are cross-sectional side views of fabric 20 havingmultiple layers. Strands such as strand 102 may be woven, knit, sewn, orotherwise incorporated into the layers of fabric 20 in the shape of aloop or set of loops, as shown in FIG. 20. This loop shape may allowstrand 102 to form a magnetic-field-based actuator structure foractuator 52. A user's finger such as finger 60 may detect movement inactuator 52 through fabric 20.

Strands such as strand 42 of FIG. 21 may be incorporated into fabric 20to form an actuator pad for actuator 52. There may be one or moreparallel strands 42 on the surface of fabric 20 (e.g., to form arectangular pad in the shape of a keyboard key or to form multi-strandactuator pads of other suitable shapes). During operation, strands 42may be contacted on the surface of fabric 20 in item 10 by user's finger60.

Actuators such as actuators 52 of FIGS. 20 and 21 may be incorporatedinto the surface of item 10, into a strap for item 10, into a handle orpocket for item 10, into a planar fabric cover layer for a keyboard initem 10, and/or into any other structure for forming item 10.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. Apparatus, comprising: a magnetic-field-basedactuator formed from a conductive strand that is coiled around a tubularstructure with a non-circular cross-sectional shape; and a controlcircuit that applies current to the conductive strand to generate amagnetic field that causes the tubular structure to acquire a circularcross-sectional shape.
 2. The apparatus defined in claim 1 furthercomprising a layer of material to which the tubular structure isattached.
 3. The apparatus defined in claim 2 wherein the layer ofmaterial comprises a layer of fabric and wherein the tubular structurecomprises piping on the layer of fabric.
 4. The apparatus defined inclaim 3 wherein the non-circular profile is an oval profile.
 5. Theapparatus defined in claim 4 wherein the oval profile is characterizedby a minor axis and a major axis that is larger than the minor axis, andwherein the major axis is parallel to the layer of fabric.
 6. Theapparatus defined in claim 1 wherein the magnetic-field-based actuatorprovides haptic feedback.
 7. The apparatus defined in claim 1 whereinthe tubular structure is formed from a material selected from the groupconsisting of: foam, fabric, and elastomeric polymer.
 8. The apparatusdefined in claim 1 further comprising an electrical component that isaligned with the magnetic-field-based actuator.
 9. The apparatus definedin claim 8 wherein the electrical component comprises a sensor andwherein the control circuit applies the current based on an output fromthe sensor.
 10. A fabric-based item, comprising: fabric formed fromstrands of material; a magnetic-field-based actuator formed from aconductive strand in the strands of material, wherein the conductivestrand forms a loop; non-conductive strands in the strands of material,wherein the non-conductive strands pass through the loop; and controlcircuitry that applies a signal to the magnetic-field-based actuator tochange a shape of the loop and generate haptic output.
 11. Thefabric-based item defined in claim 10 wherein the control circuitrychanges the shape of the loop from a non-circular shape to a circularshape in response to a user input.
 12. The fabric-based item defined inclaim 10 further comprising a keyboard having keys covered with thefabric, wherein the actuator is aligned with one of the keys. 13.Apparatus, comprising: a fabric, wherein the fabric includes first,second, and third fabric layers; a conductive thread, wherein a firstportion of the conductive thread is interposed between the first layerand the second layer and a second portion of the conductive thread isinterposed between the second layer and the third layer; and controlcircuitry that applies a signal to the conductive thread to move theconductive thread and generate haptic output.
 14. The apparatus definedin claim 13 wherein the conductive thread forms an actuator pad.
 15. Theapparatus defined in claim 14 wherein the actuator pad forms a keyboardkey.
 16. The apparatus defined in claim 14 wherein a layer of dielectricmaterial overlaps the actuator pad.
 17. The apparatus defined in claim16 wherein the dielectric material comprises elastomeric material. 18.The apparatus defined in claim 13 wherein the fabric comprises wovenfabric.
 19. The apparatus defined in claim 13 wherein the controlcircuitry applies the signal in response to a user input.
 20. Theapparatus defined in claim 13 wherein the control circuitry generatesthe haptic output in a first pattern in response to a first user inputand wherein the control circuitry generates the haptic output in asecond pattern that is different from the first pattern in response to asecond input.